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It is worth understanding the potentials of zero charge (PZCs) and structures of stepped metal/water interfaces, because for many electrocatalytic reactions, stepped surfaces are more active than atomically flat surfaces. Herein, a series of stepped Pt/water interfaces are modeled at different step densities with ab initio molecular dynamics. It is found that the structures of Pt/water interfaces are significantly influenced by the step density, particularly in regard to the distribution of chemisorbed water. The step sites of metal surfaces are more preferred for water chemisorption than terrace sites, and until the step density is very low, water will chemisorb on the terrace. In addition, it is revealed that the PZCs of stepped Pt/water interfaces are generally smaller than that of Pt(111), and the difference is mainly attributed to the difference in their work function, providing a simple way to estimate the PZCs of stepped metal surfaces. Finally, it is interesting to see that the Volta potential difference is almost the same for Pt/water interfaces with different step densities, although their interface structures and magnitude of charge transfer clearly differ. [ABSTRACT FROM AUTHOR]

Photoelectrocatalytic approaches show promise for contaminate removal in wastewater through redox reactions. However, the direct treatment of very low concentration heavy metals is a challenging task. Copper bismuth oxide is considered as a potential photocathode material due to its appropriate bandgap width and excellent light absorption properties. In this work, we utilize copper bismuth oxide photoelectrodes with micrometer-scale pores to achieve the efficient and complete reduction of micromolar-level hexavalent chromium(VI) in wastewater. In a continuous 180 min experiment, the reduction rate of 5 µM hexavalent chromium reached 97%, which is an order lower than the drinking standard. Such a process was facilitated by the unique hierarchical microstructure of the oxide thin film and the porous morphology. On the other hand, the structural evolution during the operation was analyzed. A surface passivation was observed, suggesting the possible long-term practical application of this material. This study serves as an important reference for the application of photoelectrocatalysis in addressing Cr(VI) pollution in wastewater, with implications for improving water quality and environmental protection. [ABSTRACT FROM AUTHOR]

In order to expand the application of bismuth vanadate (BiVO4) to the field of photoelectrochemistry, researchers have explored the potential of BiVO4 in catalyzing or degrading organic substances, potentially presenting a green and eco-friendly solution. A study was conducted to investigate the impact of electrolytes on the photocatalysis of benzyl alcohol by BiVO4. The research discovered that, in an acetonitrile electrolyte (pH 9) with sodium bicarbonate, BiVO4 catalyzed benzyl alcohol by introducing saturated V5+. This innovation addressed the issue of benzyl alcohol being susceptible to catalysis in an alkaline setting, as V5+ was prone to dissolution in pH 9 on BiVO4. The concern of the photocorrosion of BiVO4 was mitigated through two approaches. Firstly, the incorporation of a non-aqueous medium inhibited the formation of active material intermediates, reducing the susceptibility of the electrode surface to photocorrosion. Secondly, the presence of saturated V5+ further deterred the leaching of V5+. Concurrently, the production of carbonate radicals by bicarbonate played a vital role in catalyzing benzyl alcohol. The results show that, in this system, BiVO4 has the potential to oxidize benzyl alcohol by photocatalysis. [ABSTRACT FROM AUTHOR]

Developing stable and efficient nonprecious‐metal‐based oxygen evolution catalysts in the neutral electrolyte is a challenging but essential goal for various electrochemical systems. Particularly, cobalt‐based spinels have drawn a considerable amount of attention but most of them operate in alkali solutions. However, the frequently studied Co–Fe spinel system never exhibits appreciable stability in nonbasic conditions, not to mention attract further investigation on its key structural motif and transition states for activity loss. Herein, we report exceptional stable Co–Fe spinel oxygen evolution catalysts (~30% Fe is optimal) in a neutral electrolyte, owing to its unique metal ion arrangements in the crystal lattice. The introduced iron content enters both the octahedral and tetrahedral sites of the spinel as Fe2+ and Fe3+ (with Co ions having mixed distribution as well). Combining density functional theory calculations, we find that the introduction of Fe to Co3O4 lowers the covalency of metal‐oxygen bonds and can help suppress the oxidation of Co2+/3+ and O2−. It implies that the Co–Fe spinel will have minor surface reconstruction and less lattice oxygen loss during the oxygen evolution reaction process in comparison with Co3O4 and hence show much better stability. These findings suggest that there is still much chance for the spinel structures, especially using reasonable sublattices engineering via multimetal doping to develop advanced oxygen evolution catalysts. [ABSTRACT FROM AUTHOR]

Ga2O3 have attracted considerable attention in the field of photocatalysis. However, the preparation of 1D nanostructured Ga2O3 photocatalyst with high purity and controllable structures is still in challenge. Herein, we report the synthesis of Ga2O3 nanofibers with controllable structures by using electronspinning method and annealing treatment. The SEM, TEM, XRD and XPS results revealed that the produced Ga2O3 photocatalysts have three different morphologies, including nanofibers, nanofibers/nanobelts and nanobelts, which was obtained by tailoring the raw materials and electronspinning parameters. The photocatalytic hydrogen evolution results show that the Ga2O3 nanofibers display the highest hydrogen evolution rate among the three samples. The excellent photocatalytic performance of Ga2O3 nanofibers photocatalyst could be resulted from its larger BET specific surface area and pore volume, which can provide more active sites and shorten the charge transfer distance. We report the controlled preparation of Ga2O3 nanofibers forphotocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Cation effects have been shown in numerous experiments to play a significant role in electrocatalysis. To understand these effects at the molecular level, we systematically investigate the structures and capacitances of electric double layers with a variety of cations as counter charges at Pt(111)-COad/water interfaces with ab initio molecular dynamics. It is encouraging to find that the computed Helmholtz capacitances for different cations are in quantitative agreement with experiments, and that the trend of cation effects on capacitances shows clear correlation with the structures of interface cations of differing sizes and hydration energies. More importantly, we demonstrate the Helmholtz capacitance as the key descriptor for measuring the activity of CO-CO dimerization, the rate-determining step for C2+ formation in electroreduction of CO and CO2. Our work provides atomistic insights into cation effects on electric double layers and electrocatalysis that are crucial for optimizing electrode and electrolyte materials. [ABSTRACT FROM AUTHOR]

A photoelectrochemical (PEC) cell composed of two semiconductor electrodes, a photocathode, and a photoanode is a potentially effective means of obtaining hydrogen through spontaneous overall water splitting under light irradiation. However, the long-term stability (that is, operation for more than one day) of a PEC cell has not yet been demonstrated. In addition to the corrosion of both photoelectrodes, the gradual migration of heavy metal cations from the photoanode into the electrolyte can also result in degradation of the cell by contamination of the photocathode surface. In the present work, BiVO4-based photoanodes were used in conjunction with two different modifications: dispersion of a chelating resin in the electrolyte and coating of the photoanode surface with an anion-conducting ionomer. The chelating resin was found to capture Bi3+ cations in the electrolyte before they became deposited on the cathode surface. Consequently, a PEC cell incorporating a BiVO4-based photoanode and a (ZnSe)0.85(CuIn0.7Ga0.3Se2)0.15-based photocathode showed stable overall water splitting over a span of two days under simulated sunlight. To the best of our knowledge, this represents the longest period over which stable PEC cell performance has been established. A considerable decrease in the performance of the BiVO4-based photoanode was still observed due to the continuous dissolution of Bi species, but surface coating of the photoanode with an anion-conducting ionomer prevented the movement of Bi3+ ions into the electrolyte because of the selective conduction of ions. The coating also served as a protective layer that improved the durability of the photoanode. This study therefore suggests a simple yet effective method for the construction of stable PEC cells using semiconductor photoelectrodes. [ABSTRACT FROM AUTHOR]